daniel connolly



(NoMoael.)

M. D. CONNOLLY.

l AUTOMATIC TELEPHONE EXCHANGE.

10.263,862. Pated-sept.5,182

N. PETZRS. PhunrulIwgmpher ssssssssss C.

UNITED STATES PATENT Carien.

M. DANIEL CCNNOLLY, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO SPENCER D. SCHUYLER, OF NEW YORK, N. Y.

AUTOMATICTELEPHONE-EXCHANGE.

SPECIFICATION forming part of Letters Patent No.l 263,862, dated September 5, 1882. Application filed October 529, 1881. (No model.)

To all whom it may concern Be it known that I, M. DANL. CGNNOLLY, a citizen of the United States, residing atPhiladelphia, in the county ot' Philadelphia and State ot' Pennsylvania, have invented certain new and nsef'ul Improvements in Automatic Telephone Exchanges or Circuit Changers; and I do hereby declare the following to be a i'nll, clear, and exact description ot' the in ven- 1o tion, reference being had to the accompanying drawing, which forms part of this specitication, and which is a diagram illustrating myinvention.

`Hy invention has relation to the automatic I5 telephone-exchange system for which Letters Patent of the United States No. 222,458, dated December 9, 1879, 'were granted to myself, Thomas A. Connolly, and Thomas J. McTighe, and more particularly7 to the improvements zo thereon for which I and said parties jointly, hy application tiled August 29, '1881, applied for further Letters Patentot the United States. In said application we have shown anarrangementof parts whereby a subscribers'line leads z5 to a switching mechanism at the central station, and from said mechanism leads normally to ground or return. Further, said mechanism is so arranged that by a progressive movement, dependent upon electric impulses sent 3o over the subscribers line and operating a relay at the central station, his circuit at the central station may be changed from ground to another subscribers line, such change of circuit comprehending the automatic connection otlines. When such circuit leads to ground at the central station it is unich shorter than vwhen connection ot' lines is established, and as difference in the lengths ot' circuits produces variations in resistance therein it fol- 40 lows that the electric current flowing from a suhscribers local operating-battery meets with ditterentresistances as his circuit at the central station changes from ground to line. Still further, as the different lines leading to the central station vary in length, there is a corresponding variation in the resistance they oppose to the same electric current sent'over them, so that as one ysubscriber makes connection successively over other subscribers 5o lines hisoperating-current encounters unlike resistances in dift'erentlines.l Now, as such curt rent acts upon a relay to eit'ect the progressive movement whereby change of circuit and con l ncction ot' lines are established, and as a relay to work effectively should be adjusted to a given strength of current, and as the strength or force of such current lessens under resist-V ance, it follows that with variable resistances to meet and overcome as the progressive movement proceeds the relays action cannot be unit'orm, and that said progressive movement will be more or less faulty.

The iirs't part of my improvements relates to .this feature, and it. consists in providing an artificial resistance inthe ground or return l at the central station, so as to equalize the resistances of ground and line. The second part ot' my improvements consists in rendering lines which are unlike in length equal in resistance;V and it consists in locating in each line, except 7o the largest one, an artificial resista-nee. Thus when an exchange is organized a maximum resistance should be selected equal to or in excess ot' the resistance ot' the longest line leading thereto. Alltheshorterlincswillhaveartilicial resistances located in them, either at the central station or at the subscribers7 local stations, or at any point between the same, the'amount of resistance in each line being dependent upon l the length ot' such line, and inversely as such 8o length, so that the resistance in all lines will be equalized, producing the same effect as it' the lines were equal in length and sectional arca. In the ground or return at the central station an artificial resistance will be placed,

so as to bring the resista-neem" ground-circuit at central station up to the resistance of line. If the lines have a common ground at central station, one resistance will be sufticient; but as by the further improvements hereinafter de- 9o scribed an independent circuit to ground for each lineis necessary or expedient, a separate ground-resistance foreach such line at the central station is or may be expedient or desirable.

In operating the switching' mechanism at 95 the central station it sometimes may happen that a desired connection ot lines is not eii'ected. Thismay result from a defect ofthe working mechanism, from inaction of a subscrihers battery or the central-cttlce battery or generaroo tor, from an imperfect contact in some of the circuits, from leakage of the electric current,

Vor other cause. In such case a subscriber starts the dial mechanism at his own local box. When theindex on such dial reaches the number or symbol belonging to some other line Aze ' with any line leading thereinto.

the seeking or calling` subscriber naturally supposes he has ei'ected through the central ofee a connection with such other line, and rings a call. lhe necessary contact or connection at central station not having been effected, he fails to get any response and is ignorant ofthe reason. If the switching mechanism at the central station has for any reason failed to operate correctly, he has no means of calling up the central oflicc over his line, and so loses all power of communication over the line until the defect in his own line has been remedied. So, too,it' a subscriber seek the line of another already engaged, he cannot effect connection therewith, the contact-bar ofthe latter, during engagement, being swung out of position for contact,as fully described in thea forementioned joint application. His workingmechanism remains correct, and he has a circuit to ground which will enable him to reach homeforcall up any other line; but he is not apprised of the reason why he cannot get a particular' line he seeks but fails to connect with. Still further, subscribers may desire trom time to time to call up the central ofce for various purposes. To do this with and under the arrangement of parts shown in said joint application, it would be necessary, in order to get communication with the central station, to operate the switching mechanism at said central station to establish connection with a line or contact-bar in such mechanism assigned to the central oiiices particular use.

The third part of my improvements relates to the provision of means whereby if a subscriber fails to get, for any reason, connection with a line he seeks, the fact of Stich failure will be announced at the central station when thecalling subscriber rings for thc party he seeks and whose line he may suppose he has, so that the central office may correct such failure and establish the connection, or, in the case of a line already engaged by one party and sought Aby another, inform the calling party why the connection cannot then be had. Said improvemeu ts also relate to and comprise means whereby any subscriber may at any time and without operating the diatmechanism at his own box or local station call up the central office and be placed in communication therewith or This part of my improvements consists in the combination,

with the automatic switching mechanism at the central office, of an electric annunciator and alarm (either or both) located in the ground or return circuits of the lines leading into such mechanism, and operative by acnrrent the reverse of that which will operate the relays of suchautomatic mechanism.

Referring to the accompanying drawing, A represents an automatic exchange or switching mechanism constructed on the plan described in the aforesaid application, and which therefore need not be more particularly herein described.

B B' represent the boxes of local subscribers whose lines?) b lead to the central station.

a casca All the lines have like (though not identical) circuits at the central station, so that to follow one will be sufficient for all. The circuit of line b through the machine is shown by arrows l. It will be seen that it passes at all times through the tripper77 C, or traveling circuit-maker ot' such line, and that when such tripper is at home,7 or not in contact with any of the contact-bars l), said circuit goes -to ground or return, GL When the tripper is in contact with a bar D the circuit is shifted from ground at central station to the line to which bar l) in contact with it belongs. Now, as already remarked, as'this makes a longer circuit than to ground direct, I equalize the rcsistauces by locating au artitcial resistance, R, in the ground-circuit at the central station. When each line has a separate circuit from the machine or switch to ground -such resistance will be located in each such separate groundcircuit. As the lines vary in length, and correspondingly in resistance, l equalize all by artificial resistances in each line, as at R. Thus, for example, Vsay line 1, the longest,has a normal resistance of, say, twenty ohms, line 2 a normal resistance of, say, ifteen ohms, line 3 a normal resistance of ten ohms, and line 4 a normal resistance of only tive ohms. I equalize the resist-.luces by placing in lines 2, 3, and 4 artiticial resistances R ot' live, ten, and lifteen ohms, respectively. Now, a current passcentral station meets a resistance ot' twenty ohms; but when two lines are connected the resistance is doubled, or is, say, forty ohms. There is thus a dil'erencc of, say, twenty ohms resistance between circuit to ground at central station and over connected lines. To equalize this l locate in the ground-circuit at central station an artilicial resistance'equal to the resistance ofthe longest line. ln that imagined above it would be twenty ohms. By these meanstheresistancesthroughoutareequalized, so that the relays work uniformly, whether a subscriber is making circuit to ground at central station or over any particular line.

It' a subscriber in operating his switching mechanism fails to get a connection with a bar of another line, his circuit is to ground at central station. lt is so with all lines leading to the automatic exchange or switch A. Let each subscriber have a separate circuit to ground at the central station and these circuits lead to an annunciator, H, as shown. Each line has an electro-magnet, h, in such annuncia-tor for operating a drop.77 or shutter,77 h', therein. Each line has also, if desired, an electric bell, I; or the circuits ot' all lines may lead from their annunciator-magnets to one bell, which will thus be an alarm common to all; or the annunciator may be so constructed that the dropping ot' a shutter will close an open circuit to the bell, and thus cause the latter to ring.

The bell or bells may be dispensed with and the shutters or drops form the alarm in themselves. The' annunciator drops or shutters should be carried on polarized armatures, and

ing over any one of these lines to ground at IOO IIO

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the magnets t-hereofsoarrangedi.e.,reversely with reference to the relay magnetstliatacurrentwhich will operate said relays will not operate the drops or shutters, and vice versa.

1f a bell or bells, I, be employedpit or they inustbe polarized if in the same circuit. with the shntter-magnets, and the same arranginent relative to the relaybe preserved-t'. e., the bellmagnet or magnets t must attract their armatures to ring by a current the reverse of that which operates .the relay. The reason is this: In the progressive movement of the tripper the circuit is always through the relay and i alternately to groniid at central station and Y ment the curreiitis of one. direction, so as to operate the relay. Vere the annunciator and bell in ground-circuit at central station capable of being operated by aucurrent of the samedirection, the moment the current became shifted from line toigrouiid in making the progressive movement said annunciator and bell would be This is not desirable. Hence the til the current over line is reversed by a subscriber (which reversal takes place when a subscriber rings after having ceased the progressive movement.) is the annunciator or bell in the central groniid-circuit operated.

In the groundeircuit of each line at central station, or in shunts thereof, there are means for placing a telephone or telephones pioperly in line, together wit-h a battery or generator for sending back over the line a current of such direction as not to effect alnovenientof the relay in such line, yet to ring the bell of the subscriber at his own box or station.

K represents the telephone; K', its switch; L, the battery, and N a push-button for these purposes.

rlheoperation therefore is as-foilows: A subscriber manipulates his box or dial instrument to effect connection with another line, and then rings by a reversed current. If the sought connection has been established at the central oice, the alarm is sent over the connected lines without affecting any of the parts at such central office. If, however, from any cause such connection.. has not been effected, the seeking or calling subscriber has then a ground or return circuitat central station. .Vhen lie rings by his reversed current the annunciator drop or shutter and .the bell which are in said ground or return circuit are operated, thus indicating that a subscriber has failed to make a desired connection, and further notifying the central oftce who such subscriber is. The central-office attendant thereupon throws the required battery on the line ot' such subscriber, and sends back an alarm by a current which will not work the polarized relay in circuit, puts a telephone or telephones (transmitter and receiver) into the circuit, and thus learns who it is the subscriber seeks to connect with. Having learned this he establishes the connecv Y tion between the seeking and the sought'line,

'at the central office.

4either by direct manual operation or by working the calling subscribers relay, thus making the circuit direct over both lines, the annunciator, 85e., in the central ground-circuits of such lines being cut out in forming the connection. So, too, if asubscriber seek another. and ring when he thinks he has effected connection therewith, if such other be already engaged and his contact-bar D be swung out so that such connection cannot be obtained, as

such seeking subscriberhas his ground-circuit atcentral office, such ringing will notify the central office, 4as before described, and the latter will be able to notify the calling party ofthe en-A gagement which prevents his getting communication with the party he seeks. Still further, if asubscriber wishes at any time to call Centra-l station without operating his dial-instrument, all he has to do is to merely ring in the usual manner-that is, by sending a reversed current frein his own box over his line. His tripper at the central station being in its home position, his circuit there is to ground. The aiiuunciator and bell there, heilig' in such ground-circuit, are operated by such reversed current, as already described in the cases where his tripper has left home to seek another lineJ but failed to 'get it.

As normally there is no electrical current in the ground-circuits at the centra-l station, the annunciator should be so constructed that its drop or shutter .will be moved so as to be broughtinto display position when its magnets are energized by currents of the proper direction. If desired, the ground-resistance inentioned as the first part of my improvement niay-be constructed of the annunciator or bell magnets (either or both) in the ground-circuits Adispensed with, the lines at central station all have a common ground, and a bell be placed in this ground. Under this arrangement the central station may be called by any subscriber without operating the dial mechanism of his box, and failures to effect connection will be notified through the same means. In such latter case the central office has to look up the missed connection, whereas with the aiinuiiciator drops or shutters the failing or calling line is designated. Hence as an annunciator without a bell or a bell without drops or shutters may be employed, my invention embraces either or both arrangements, the term alarm including both. I have shown such alarm and the equalizing resistances combined `with the particular automatic switch mechanism illustrated and referred to; but my claims are not restricted thereto, and are intended to inlar switching mechanisui.

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What Iclaim as myinvention is as follows: mechanism, substantially as shown and de- 1. In a circuit-changer or exchange-switch having means for changing circuit from ground or return to different lines, the combination, with the ground-connection,of artificial resistance therein to equalize it-with line, substantially as set forth.

2. In an exchange system comprising a series of convergent or divergent lines leading to or from a central office or station switch, the combination, with the lilies and switch, of art-iticial resistances in such lines to equalize the latter, substantially as set forth.

3. In an exchange system comprising a series of convergent or divergent lines leading to or from a central office or station switch and normally grounded thereat, the combination, with such switch and the ground and line circuits, of artificial resistances in such circuits to equalize the same, substantially as set forth.

4. In combination with an automatic exchange or switch operating by a progressive movement to establish connection between` normallyindependent lines, and which, in effecting such movement, changes circuit from ground or return to line, resistances in such ground or return and line circuits to equalize the resistance ot' such circuits, substantially as set forth.

5. 1n a circuit-changer or exchange comprising means for effecting connection of normally independent lines by a progressive or step-by-step movement controlled by impulses sent through a relay, and operating a traveling circuit-maker which alternately shifts from ground toline, the combination, with such relay and traveling circuit-maker, of circuits having their' resistances equalized by means substantially as described.

6. 'Ihe combinatiomwith an automatic switch Whose lines are normally grounded ator return from a central office, of an annunciatoror alarm (either or both) located in such ground or return circuit at the central office, substantially as and for the purpose set forth. Y

'7. The combination, with an automatic cxchange, switch, or circuit-changer which operates to effect connection of normally-independent lines by a progressive or step-by-step movement, and which,in operating, changes circuit from ground or return to line, ot' an annunciator or alarm. located in the ground or return circuit to notify the central oicc of failures to establish connection of lines, or to call up said central office without operating the switching scribed.

8. The combination, with an automatic telephone exchange or switch which operates bya progressive or step-by-step movement to effect connection of normally-independent lines, and which, to efi'ectsaid connection, causes a circuitmaker to travel from line tolineand alternately to shift circuit from ground to said lines, and vice versa, said movement being controlled by electric impulses sentoverline th rough a polarized relay, of a polarized annunciator or alarmlocated in or connected with thevground or return circuits of said exchange or switch, and arranged to operate responsively only to a current the reverseof thatwhich will operate said relay, as set forth.

9. The combination of an automatic switch or progressive or step-by-step movement circuit-changer, an annuciator in the ground or return circuit thereof, a telephone in a shunt or normally cut-out branch, a battery or getierator, and means for throwing the same onto line in such circuit, whereby the central office can be called without operating the automatic switch, or will be notified automatically of failure of any attempt to connect lines through the automatic switch, and can send an alarm and communicate over the line with the seeking subscriber to learn and supply his wants, substantially as set forth.

10. ln an exchange comprising a series ot' lines converging to a central office or station,4

and connected with switching mechanism at such office, where they are normally grounded, or whence they normally return, said lines being connected at their outward termini with boxes having appliances whereby may be sent currents of one direction to operate the switching mechanism and currents of opposite direction to ring an alarm without operating the switching mechanism, the combination, with such switching mechanism, boxes, and connections, of an annnnciator or alarm located in the ground circuit or circuits of the lines at the central office, and operative by currents which will not actuate the switching mechanism, substantially as set forth. A

In testimony that I claim the foregoing I have hereunto set my hand this 27th day of October, 1881.

- M. DANL. OONNOLLY. Witnesses S. J. VAN S'rAVoREN, Unas. F. VAN HORN.

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